A surgical stapling device includes a tool assembly having an anvil and a cartridge assembly that are movable in relation to each other between open and clamped positions. The cartridge assembly includes a staple cartridge that can be replaced after each firing of the stapling device to facilitate reuse of the stapling device. The anvil includes a lockout mechanism that prevents operation of the stapling device when the staple cartridge has been previously fired. The lockout mechanism moves from a locked position to an unlocked position in response to movement of the tool assembly from the open position to the clamped position.